Rotor comprising a spoked wheel-like balancing disc for providing cooling ducts
The spoked balancing disc with integrated coolant channels addresses the instability and space challenges of existing electric motors by enhancing the rotor's stability and cooling efficiency, reducing complexity and space usage.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- MAHLE INT GMBH
- Filing Date
- 2025-11-19
- Publication Date
- 2026-06-04
AI Technical Summary
Existing electric motors face challenges in securing a stable connection of the balancing disc to the rotor shaft, leading to potential instability, especially at higher speeds, and require separate coolant channels that increase complexity and space usage.
A rotor with a spoked balancing disc that integrates coolant channels, providing a robust connection to the rotor shaft through positive and/or force-fit connections, eliminating the need for a separate coolant system and enhancing cooling efficiency by increasing coolant flow cross-section.
The integrated balancing disc improves the rotor's stability and cooling performance while reducing component count and installation space, achieving a homogeneous cooling effect and targeted anomaly response.
Smart Images
Figure EP2025083558_04062026_PF_FP_ABST
Abstract
Description
[0001] Rotor comprising a spoke-shaped balancing disc to provide cooling channels
[0002] The present invention relates to a rotor for an electric machine, preferably a separately excited or electrically excited synchronous motor. In particular, the present invention relates to a rotor comprising a spoke-shaped balancing disc for providing cooling channels. Furthermore, the present invention relates to an electric motor comprising such a rotor, an electric axle drive with such an electric motor, and an at least partially electrified vehicle with such an electric axle drive.
[0003] Electric axle drives for purely electric vehicles and hybrid electric vehicles are well known from the prior art. Such drive systems generally comprise an electric motor with a stator and a rotor rotatably mounted in the stator. The stator has several phase strands designed as stator windings, each of which is supplied with a corresponding phase current during operation. The phase currents are phase-shifted from one another, such that the current flowing through the stator windings creates a rotating magnetic field. The rotor has a rotor shaft and a rotor core that is fixed to the rotor shaft and is magnetically active. The magnetic interaction between the rotor core and the rotating field on the stator side generates a torque that sets the rotor in rotation.
[0004] It is known from the prior art to provide a balancing disc in the electric motor, which is generally mounted on the end face of the rotor core, in order to balance the rotor or the electric motor as a whole, particularly at higher speeds. Such a balancing disc is disclosed, for example, in CN 202737652 U. The balancing disc can include several recesses for providing a negative counterweight. However, known electric motors have disadvantages regarding the mounting of the balancing disc on the rotor, in that, due to the design of the balancing disc, a sufficiently secure connection of the latter to the rotor shaft is not guaranteed. According to the invention, the aforementioned problem is solved by the rotor, the electric motor, the electric axle drive, and the vehicle according to the independent claims. Advantageous embodiments and further developments of the invention are described in the dependent claims.
[0005] In a first aspect of the present invention, a rotor for an electric machine is proposed. The electric machine is specifically a separately excited synchronous motor (PSM) or an electrically excited synchronous motor (FSM). The motor comprises a stator and the rotor rotatably mounted in the stator. The stator has several stator windings that form phase strands of the multiphase electric motor. During operation, each stator winding is supplied with a corresponding phase current, which is phase-shifted from one another. In this way, the current supplied to the stator windings causes a rotating magnetic field. The phase currents are generally generated by means of a DC / AC inverter, which converts a DC input voltage provided by a DC power supply (e.g., a battery) into an AC output voltage.The DC / AC inverter comprises several semiconductor-based power switches connected as half-bridges, which are closed and opened according to a predefined duty cycle.
[0006] The rotor has a rotor shaft that can rotate about an axis of rotation and a rotor core that is fixed to the rotor shaft. The rotor core is designed to interact magnetically with the rotating stator magnetic field. For this purpose, at least one rotor magnet, such as a permanent magnet in the case of a permanent magnet synchronous motor (PMSM) or a rotor coil with a corresponding winding in the case of a permanent magnet synchronous motor (PMSM), is attached to the rotor core. The rotor core may have a laminated core, which can be designed as an arrangement of laminated sheet metal parts.
[0007] The rotor also features a balancing disc mounted on one end face of the rotor core. The balancing disc is spoked and comprises several spokes. Between the spokes, particularly between adjacent spokes, are several openings distributed along the circumference of the balancing disc. These openings allow for the insertion of a balancing mass to negatively balance the rotor or electric motor. The spoked design of the balancing disc increases its stiffness under radial load, resulting in improved robustness of the rotor's connection to the rotor shaft and thus making it suitable for higher operating speeds.
[0008] At least one of the spokes is designed to provide a coolant channel for guiding a coolant to flow through the rotor. Preferably, several, and more preferably all, spokes of the balancing disc are designed to provide multiple coolant channels. The coolant channel(s) is / are shaped such that the coolant flows in one direction from the area surrounding the rotor into the interior of the rotor core through at least one of the openings in the balancing disc. Alternatively or additionally, the coolant can flow in the opposite direction, i.e., from the interior of the rotor core into the area surrounding the rotor, through the at least one opening in the balancing disc.
[0009] According to the invention, an effective coolant channel system is provided in a simple manner. In particular, the use of the balancing disc as at least part of the coolant channel system results in a reduction in the number of components, thus reducing the manufacturing effort of the rotor or the entire electric motor. The elimination of a separate coolant channel system also achieves a significant saving in installation space. Furthermore, the openings formed in the balancing disc allow for an increased flow cross-section for the coolant line, which also has a positive effect on the cooling performance of the rotor or the entire electric motor.
[0010] According to one embodiment, the balancing disc comprises a balancing ring connected to an inner ring via the spokes, the inner ring being positively and / or force-fit connected to the rotor shaft. This measure enables a particularly robust connection of the balancing disc to the rotor shaft, thus improving the functionality of the balancing disc with regard to balancing and cooling the rotor. According to another embodiment, the balancing disc has a connecting element that provides a positive fit with a slotted locking wedge and / or a winding carrier of the rotor. This measure increases the strength of the connection between the balancing disc and the other components of the rotor or the electric machine. Alternatively or additionally, the balancing disc can be attached to the winding carrier by means of a tie rod and / or press fit.
[0011] According to a further embodiment, the rotor core or the lamination stack of the rotor core can be positively and / or force-fit connected to the balancing disc or balancing ring. In this way, a robust connection of the balancing disc to the rotor shaft, which is rotationally fixed to the rotor core, is also established via the rotor core.
[0012] According to another embodiment, the balancing disc is designed to direct the coolant towards the slot locking wedge of the rotor. This allows the coolant to penetrate the interior of the rotor core to a greater depth, thus distributing the cooling power more effectively to the components mounted there.
[0013] According to another embodiment, the balancing disc simultaneously serves as a winding carrier for attaching a rotor winding. This eliminates the need for a separate winding carrier, resulting in further space savings.
[0014] According to another embodiment, the rotor has two spoke-shaped balancing discs attached to two opposing axial end faces of the rotor core. This extends the advantages described above in connection with a single balancing disc accordingly.
[0015] According to a further embodiment, at least one of several first openings of a first of the two balancing discs functions as a coolant inlet and / or at least one of several second openings of a second of the two balancing discs functions as a coolant outlet. The coolant inlet and the coolant outlet are thus arranged on the axially opposite end faces or face faces of the rotor core. This provides one or more axially extending cooling channels with maximum flow cross-section.
[0016] According to a further embodiment, the first balancing disc and the second balancing disc have several pairs of openings, each pair comprising a first opening and a second opening axially aligned with it, and each pair of openings being assigned to one of several coolant channels. The coolant channels can be fluidly isolated from one another, so that the coolant flowing in one coolant channel does not enter another. Alternatively, at least two, and in particular all, of the coolant channels can form interconnected sections of a single coolant channel, such that the coolant supplied to the rotor core via the coolant inlet is extracted from the rotor core via the coolant outlet after passing through the interconnected coolant channels. This measure enables a particularly uniform distribution of the cooling capacity within the interior of the rotor core.
[0017] According to another embodiment, the coolant channels define two opposing coolant flow directions. For example, adjacent coolant channels can define two opposing coolant flow directions, whereby the adjacent coolant channels can be connected in series or, alternatively, separated from each other. This measure prevents the interior of the rotor core from being cooled differently in the regions of the axial end faces, thus achieving a homogeneous cooling effect.
[0018] According to a further embodiment, at least one of the coolant channels is adjustable with respect to a coolant flow parameter based on condition monitoring of the at least one coolant channel and / or a component of the electric motor, in particular a magnet, preferably a rotor coil, located in a region of the at least one coolant channel. The condition monitoring can be carried out by means of a plurality of measuring units, each of which detects a condition parameter (or a set of condition parameters comprising several condition parameters), such as temperature, rate of change of temperature, current, and / or rate of change of current of an associated coolant channel or of the component located in the coolant channel (such as the associated rotor coil). This means that there is a one-to-one correspondence between the measuring units and the coolant channels.If one of the measuring units detects an anomaly, for example, if the value of a monitored condition parameter exceeds a predefined threshold, a corresponding warning signal can be generated. A central control unit for controlling at least one coolant flow parameter, such as flow rate and / or flow cross-section, of the coolant channels receives the warning signal and then adjusts the coolant flow parameter of the coolant channel associated with the measuring unit that detected the anomaly. This process can be performed iteratively, with the monitored condition parameter of the affected coolant channel or the associated component being compared again with the predefined threshold after each iteration. The iterative process can be terminated when the monitored condition parameter is equal to or below the predefined threshold.This allows for targeted responses to local anomalies in the coolant channels and timely corrective action to rectify the anomaly without affecting other areas of the rotor core's interior. Furthermore, this minimizes data processing overhead.
[0019] According to a further aspect of the present invention, an electric machine, in particular a separately excited synchronous motor, is proposed, comprising a stator and a rotor according to one of the embodiments described in this disclosure. According to yet another aspect of the present invention, an electric axle drive for an at least partially electrified vehicle is proposed, comprising such an electric motor and an inverter for supplying power to the electric motor. According to yet another aspect of the present invention, a vehicle with such an electric axle drive is proposed.
[0020] The advantages already described in connection with the rotor according to the invention also apply to the electric machine, the electric axle drive, and the vehicle according to the invention. The features of the claims and those described above and below with reference to the drawings complement each other. Features that become apparent in the exemplary embodiments, both individually and in each combination, advantageously further define the subject matter of the claims and also the embodiments described above.
[0021] The invention is explained below by way of example with reference to embodiments shown in the figures. The figures show:
[0022] Fig. 1 shows a schematic representation of a vehicle comprising an electric axle drive;
[0023] Fig. 2 shows a schematic representation of a rotor of the electric axle drive, on which a balancing disc is attached to the end face of a rotor core;
[0024] Fig. 3 shows a schematic representation of the rotor with the balancing disc mounted on the front face according to one embodiment in a perspective view;
[0025] Fig. 4 shows a schematic representation of the balancing disc from Fig. 3 in a further perspective view;
[0026] Fig. 5 shows a schematic representation of the rotor with two balancing discs mounted on the end face, showing a coolant channel system according to one embodiment;
[0027] Fig. 6 shows a schematic representation of the rotor with two balancing discs mounted on the end face, and a coolant channel system according to a further embodiment;
[0028] Fig. 7 shows a schematic representation of the rotor with two balancing discs mounted on the end face, and a coolant channel system according to a further embodiment; Fig. 8 shows a schematic representation of a control unit for controlling coolant flow parameters of several coolant channels in the coolant channel system based on the detection of state parameters of the coolant channels by several measuring units.
[0029] Identical objects, functional units, and comparable components are designated across all figures using the same reference symbols. These objects, functional units, and comparable components are identical in their technical characteristics unless explicitly or implicitly stated otherwise in the description.
[0030] Fig. 1 shows a schematic representation of a vehicle 100 that is at least partially electrified. The vehicle 100 can be a purely electric vehicle or a hybrid vehicle. The vehicle 100 is equipped with an electric axle drive comprising an electric motor 102, a DC / AC inverter 106, and a gearbox 112. The electric motor 102 comprises a stator with several phase strands arranged as stator windings and a rotor 116 (see, for example, Fig. 2) with a rotor shaft 120 rotatably mounted about an axis of rotation 124, and a rotor core 118 non-rotatably connected to the rotor shaft 120. The rotor core 118 is preferably rotationally symmetrical with respect to the axis of rotation 124. The inverter 106 is connected between the drive battery 106 and the electric motor 102 for the purpose of converting a DC input voltage provided by a drive battery 104 into an AC output voltage.For this purpose, the inverter 106 has a plurality of power switches (not shown in detail here) that form a bridge circuit with several half-bridges and can be controlled by control signals generated by a control unit 108. The control signals are preferably configured to switch the power switches of the inverter 106 according to pulse width modulation (PWM). In particular, opening and closing the power switches generates several preferably sinusoidal and phase-shifted phase currents for each of the phase strands of the stator of the electric motor 102. The phase currents, which are each fed into one of the several phase strands of the stator, cause a rotating magnetic field in the interior of the stator. The rotor core 118 is magnetically active by the fact that at least one permanent magnet in the case of a permanent magnet synchronous motor (PSM) or an electromagnet is embedded in the rotor core 118.A rotor coil is mounted in the case of a separately excited / electrically excited synchronous motor (FSM). This results in a stationary magnetic field. Based on the interaction between the rotating stator magnetic field and the stationary rotor magnetic field, a torque is generated, which is transmitted by means of the gearbox 112, preferably a reduced-ratio gearbox, to an axle 110, here by way of example the rear axle of the vehicle 100, and finally to wheels 114, here by way of example rear wheels. The rotor 116 is shown in Fig. 2 purely schematically and by way of example. A balancing disc 126 is also shown there, which is attached to an axial end face or face of the rotor core 118. The balancing disc 126 is able to balance the rotor 118 by means of recesses or by removing a balancing mass, which increases the stability of the rotor 116 and thus also of the entire electric motor 102, especially at high speeds in ferry operation.
[0031] Fig. 3 shows the rotor 116 according to a further embodiment in a purely schematic and exemplary perspective view. The rotor core 118 is designed as an arrangement of laminated sheet metal parts, with several rotor coils 134 being attached in the rotor core 118. After installation in the rotor core 118, these coils are closed by means of several axially extending slot locking wedges 119. The electric motor 102 is thus a FSM (Functional Stability Module). The rotor 116 is provided with a balancing disc 126, 140 at both of its axial end faces / faces, with both balancing discs 126, 140 being identical in construction. A separate perspective view of the first balancing disc 126 shown on the right in Fig. 3 is shown in Fig. 4. As can be seen there, the balancing disc 126 is designed in the shape of a spoked wheel and has a plurality of circumferentially distributed openings 138, each of which is formed between two adjacent spokes 132.The balancing disc 126 is provided here as a balancing ring with an outer ring 128 and an inner ring 130, with the spokes 132 connecting the outer ring 128 to the inner ring 130. As can be seen in Fig. 3, the inner ring 130, with a central opening 136, is positively and / or force-fit connected to the rotor shaft 120 or to a projection 122 of the rotor shaft 120, which extends axially through the central opening 136 beyond the end face of the rotor core 118. The arrangement of the balancing disc 126 on the rotor core 118, as well as the arrangement of the spokes 132, and thus also the arrangement and number of openings 138, is selected such that the openings 138 and the rotor coils 134 overlap each other in the axial direction. The balancing disc 126 can simultaneously function as a winding carrier for attaching the rotor coils 134, so that no separate winding carrier is required and a saving of installation space can be achieved.
[0032] In this way, the balancing disc 126 is designed to provide or accommodate several coolant channels. In particular, the spokes 132 define the openings 138 such that at least one of the openings 138 / all openings 138 each provide a coolant channel 139a-d (see Figs. 5-7) for guiding a coolant for flowing through the rotor 116. The coolant channels 139a-d are shaped such that the coolant passes through at least one of the openings 138 of the balancing disc 126 in a conveyance direction from the surroundings of the rotor 116 into an interior of the rotor core 118. Alternatively or additionally, the coolant can pass through the at least one opening 138 of the balancing disc 126 in a reverse conveyance direction, i.e., from the interior of the rotor core 118 into the surroundings of the rotor 116. The coolant is preferably directed towards the groove locking wedges 119.In this way, an effective coolant channel system has been created. By using the balancing disc 126 as at least part of the coolant channel system, a reduction in components is achieved, thus reducing the manufacturing effort of the rotor 116 and / or the entire electric motor 102. Furthermore, the openings 138 formed in the balancing disc 126 allow for an increased flow cross-section to the coolant line, which also has a positive effect on the cooling performance of the rotor 116 and / or the entire electric motor 102.
[0033] Figures 5 to 7 each show a schematic and purely exemplary representation of the rotor 116, wherein a (first and second) balancing disc 126, 140 is attached to each of the axial end faces or front faces of the rotor 116. Both balancing discs 126, 140 are identical in construction and have a spoked wheel shape. Thus, both balancing discs 126, 140 each have a plurality of openings 138a-d, 142a-d. The balancing discs 126, 140 are aligned axially with each other such that several pairs of openings are formed, each with a first opening 138a-d of the first balancing disc 126 and a second opening 142a-d of the second balancing disc 140 that axially overlaps with this first opening. Each pair of openings is assigned a corresponding coolant channel 139a-d, which runs connecting between the corresponding first opening 138a and the corresponding second opening 142a.
[0034] The openings 138a-d and 142a-d therefore function as coolant inlets or coolant outlets (indicated in Figs. 5-7 by arrows outside the coolant channels 139a-d). Depending on the choice of the openings 138a-d and 142a-d, the coolant channel system can be configured differently with respect to coolant flow within the rotor core 118. The coolant channel system shown schematically in Fig. 5 comprises several coolant inlets provided by the first openings 138a-d, while several coolant outlets are provided by the second openings 142a-d. The connecting coolant channels 139a-d are preferably fluid-isolated from each other and thus do not exchange coolant. Additionally, the coolant channels 139a-d define a uniform coolant flow direction (indicated in Fig. 5 by arrows inside the coolant channels 139a-d). The coolant channel system shown in Fig.The coolant channel system shown schematically in Figure 6 also includes several coolant inlets and outlets. In contrast to the embodiment shown in Figure 5, the coolant inlets and outlets are distributed between the first openings 138a-d and the second openings 142a-d, such that adjacent coolant channels 139a-d define two opposing coolant flow directions. As in the embodiment shown in Figure 5, the coolant channels 139a-d are fluid-isolated from one another. This measure prevents the interior of the rotor core 118 from being cooled with different cooling capacities in the regions of the two axial end faces, thus achieving a homogeneous cooling effect. In the embodiment shown in Figure 5, the coolant channels 139a-d are fluidly isolated from one another.In the schematic and purely exemplary embodiment shown in Figure 7, the coolant channels 139a-d form sections of an identical coolant line connected in series, with adjacent coolant channels 139a-d connecting to one another at an axial end. In Figure 7, the coolant channels 139a-d are rectangular in the connection areas between adjacent coolant channels 139a-d. However, this purely schematic and exemplary geometry serves only to illustrate the embodiment shown and does not limit the present invention.
[0035] Preferably, at least one of the coolant channels 139a-d is adjustable with respect to a coolant flow parameter (such as flow rate and / or flow cross-section) based on condition monitoring of the at least one coolant channel 139a-d and / or a component of the electric motor 102 arranged in a region of the at least one coolant channel 139a-d, in particular a magnet, preferably a rotor coil 134 in the case of an externally / electrically excited synchronous motor (EESM). Fig. 8 shows a schematic representation of a control unit 144 for controlling coolant flow parameters of the coolant channels 139a-e based on the acquisition of condition parameters of the coolant channels 139a-e by several measuring units 146a-e.The measuring units 146a-e are each configured to detect one state parameter (or a set of state parameters comprising several state parameters), such as temperature, rate of change of temperature, current, and / or rate of change of current of an associated coolant channel 139a-e or of the component arranged in the coolant channel 139a-e (such as the associated rotor coil 134). This means there is a one-to-one correspondence between the measuring units 146a-e on the one hand and the coolant channels 139a-e on the other. If a measuring unit 146b (highlighted with a dashed line in Fig. 8), for example, if the value of a monitored state parameter exceeds a predefined threshold, the measuring unit 146b generates a corresponding warning signal.The control unit 144, which serves to control at least one coolant flow parameter and is preferably integrated into the control unit 108 of the vehicle 100, receives the warning signal and subsequently adjusts the coolant flow parameter of the coolant channel 139b (also highlighted with a dashed line in Fig. 8) to which the measuring unit 146b detecting the anomaly belongs. This process can be performed iteratively, with the monitored state parameter of the affected coolant channel 139a-e or the associated component being compared again with the predefined threshold after each iteration. The iterative process can be terminated when the monitored state parameter is equal to or below the predefined threshold.In this way, local anomalies in the coolant channels 139a-e can be specifically addressed, and corrective measures can be taken in a timely manner to rectify the local anomaly without affecting other areas of the rotor core interior 118. This also minimizes the data processing effort.
[0036] Reference list Vehicle Electric motor Traction battery DC / AC inverter Control unit Axle / Rear axle Gearbox Wheels Rotor Rotor core Keyway Rotor shaft Projection Axis of rotation First balancing disc Outer ring Inner ring Spokes Rotor coil Central opening First openings ae Coolant channels Second balancing disc ae Second openings Control unit ae Measuring units
Claims
Patent claims 1. Rotor (116) for an electric machine (102), in particular for a separately excited synchronous motor, comprising: a rotor shaft (120) rotatable about an axis of rotation (124) of the electric machine (102); a magnetically acting rotor core (118) arranged non-rotatably to the rotor shaft (120); a balancing disk (126, 140) attached to an end face of the rotor core (118), wherein the balancing disk (126, 140) is designed in the shape of a spoked wheel with several spokes (132) and openings (138, 138a-d, 142a-d) arranged between the spokes (132) and distributed in a circumferential direction; wherein at least one of the spokes (132) is designed to provide a coolant channel (139a-e) for the flow of a coolant through the rotor (116) such that the coolant passes through at least one of the openings (138, 138a-d, 142a-d) into an interior of the rotor core (107) and / or vice versa.
2. Rotor (116) according to claim 1, wherein the balancing disk (126, 140) comprises an outer ring (128) which is connected to an inner ring (130) by the spokes (132), wherein the inner ring (130) is positively and / or force-fit connected to the rotor shaft (120).
3. Rotor (116) according to claim 1 or 2, wherein the balancing disc (126, 140) has a connecting element which provides a positive fit with a slot locking wedge (119) and / or a winding carrier of the rotor (116).
4. Rotor (116) according to one of the preceding claims, wherein the rotor core (118) has a laminated core which is positively and / or force-fit connected to the balancing disk (126, 140).
5. Rotor (116) according to one of the preceding claims, wherein the balancing disk (126, 140) is configured to direct the coolant towards a slot locking wedge (119) of the rotor (116).
6. Rotor (116) according to one of the preceding claims, wherein the balancing disk (126, 140) simultaneously functions as a winding carrier for attaching a rotor coil (134) of the rotor (116).
7. Rotor (116) according to one of the preceding claims, wherein the rotor (116) has two spoke-wheel-shaped balancing disks (126, 140) which are attached to two opposing axial end faces of the rotor core (118).
8. Rotor (116) according to claim 7, wherein at least one of several first openings (138a-d) of a first balancing disk (126) serves as a coolant inlet and / or at least one of several second openings (142a-d) of a second balancing disk (140) serves as a coolant outlet.
9. Rotor (116) according to claim 8, wherein the first balancing disk (126) and the second balancing disk (140) have several pairs of openings, wherein the pairs of openings each comprise a first opening (138a-d) and a second opening (142a-d) axially aligned therewith, wherein the pairs of openings are each assigned to one of several, preferably fluid-insulated, coolant channels (139a-e).
10. Rotor (116) according to one of the preceding claims, wherein the coolant channels (139a-e) define two mutually opposing coolant flow directions.
11. Rotor (116) according to one of the preceding claims, wherein adjacent coolant channels (139a-e) define two mutually opposing coolant flow directions.
12. Rotor (116) according to one of the preceding claims, wherein at least one of the coolant channels (139a-e) is based on a condition monitoring of the at least 17 a coolant channel (139a-e) and / or a component of the electric machine (102) arranged in a region of the at least one coolant channel (139a-e), in particular a magnet, preferably a rotor coil (134), is adjustable with respect to a coolant flow parameter.
13. Electric motor (102) for an at least partially electrified vehicle (100), in particular a separately excited synchronous motor, comprising a rotor (116) according to one of claims 1 to 12, and a stator.
14. Electric axle drive for an at least partially electrified vehicle (100), comprising an electric motor (102) according to claim 13 and an inverter (106) for powering the electric motor (102).
15. Vehicle (100) comprising an electric axle drive according to claim 14.